The energy industry uses specialized tools and equipment to extract crude oil and gas located beneath the surface of the earth. A commonly used term for the technology used for this type of energy extraction is called downhole extraction technology. Special steel pipes, called casings, which can range in length from a few meters to several hundred meters, are joined together and inserted into boreholes, also called wellbores, bore wells, oil wells, or simply wells. They can be several kilometers deep. The main function of the casing is to separate well fluids from formation fluids, and prevent the wellbore from collapsing. The holes can be a meter or more wide on the surface and then shrink to several inches toward the bottom of the well. Some coiled-tubing wells are much smaller—on the order of 2-4 inches (5-10 cm).
During the drilling process and throughout the duration of the extraction project, telemetry sensors, often referred to simply as sensors, are used to monitor the wells. They can be placed at regular intervals on or near the casing, in the drill string and/or near the drill bit for the purpose of transmitting telemetry data to the surface station. The telemetry data, including accelerometer measurements (including direction), vibration, pressure, magnetic field measurements (including direction) and temperature, etc., are transmitted to the surface stations wirelessly using radio frequency (RF) signals, through wires, or acoustically. Since the telemetry data is crucial for ensuring the accuracy of drilling direction and location and the health of the well, it is necessary to ensure that the sensors function properly and reliably over the duration of energy wells, which could be several years.
The sensors are sometimes battery powered. This presents challenges, however. One main cause of sensor failure is rooted in batteries running out of capacity to power the sensors. One cause of premature battery failure is the high temperature inside the well, which could exceed 300° C. (or 573.15 K).
Another, possibly complimentary, approach to powering downhole sensors involves transmitting power from an external source. U.S. Pat. No. 9,103,198 B2, issued to Gonzales et al., 2015, discloses a system that uses the casing and wellstring pipe as an electrode pair to supply power to sensors and receive transmissions from the sensors. U.S. Pat. No. 8,106,791 B2 (Thompson et al., 2012), U.S. Pat. No. 8,390,471 B2 (Coates et al., 2013), U.S. Pat. No. 7,504,963 B2 (Hall, et al., 2009), and U.S. Pat. No. 6,515,592 B1 (Babour et al., 2003) disclose similar systems where casing and other nearby objects, which could be externally inserted, such as a wellstring, are used to deliver power to the sensors and receive signals emitted from those sensors.